1. Exit Choose to view chapter section with a click on the section heading. ►The Universe, Solar System, and EarthThe Universe, Solar System, and Earth ►The Origins of LifeThe Origins of Life ►Ocean Zones and LifestylesOcean Zones and Lifestyles Chapter Topic Menu

2. MenuPreviousNext 3 - 2 We Are Not Alone nWhere did Earth, the solar system, and the stars come from? Where did life come from?  When we ask these questions, we are really asking where did we come from. Origin of the Universe nOur universe began as a concentrated single point, containing all known matter and energy.  Approximately 3.7 billion years ago this single point began to expand – an event known as the Big Bang.  The universe has been expanding ever since. nMatter is not distributed uniformly throughout the universe.  A natural property of matter, gravity, began attracting helium and hydrogen atoms together.  As the density increased, matter collapsed and compacted under its own weight, causing a warm, dense core called a protostar. The Universe, Solar System, and Earth Chapter 3 Pages 3-1 to 3-5

3. MenuPreviousNext 3 - 3 Origin of the Universe (continued) nThe theorized “life cycle” of a star:  The nuclear fusion reaction from protostars creates stars.  The star burns for millions of years, consuming it’s hydrogen.  Heavy elements form as hydrogen atoms fuse during the “life-cycle” of a star.  The core becomes denser and eventually collapses under the extreme gravity forces generated by the density.  The star may explode causing a supernova.  Supernova explosions account for the distribution of heavy elements through- out the universe. The Universe, Solar System, and Earth Chapter 3 Pages 3-4 & 3-5

4. MenuPreviousNext 3 - 4 Origin of the Solar System nThe sun, Earth, and other planets in the solar system are only one of the millions of such systems that make up the Milky Way Galaxy.  The current theory of how our solar system formed, with the planets orbiting the sun, began with a large cloud of hydrogen and helium called a nebula.  A shock wave from a supernova caused the cloud to condense, which caused it to spin.  As the cloud collapsed and became denser, it flattened in a disk due to the rotation. At the center a protostar developed and began the nuclear fusion process, becoming the sun. nSome gas continued to revolve around the sun, eventually condensing into masses too small to become stars – they became the planets.  This theory that the solar system originated as a nebula is called the nebular theory. The Universe, Solar System, and Earth Chapter 3 Pages 3-5 & 3-6

5. MenuPreviousNext 3 - 5 Origin of the Earth… nAccording to nebular theory, Earth (and other solar system planets) formed through accretion.  Accretion is the process by which small particles clump together because of gravity. As a mass grows the more gravity it has, the more additional mass it attracts.  The Earth’s growing mass caused its core to compress causing the core to heat and become molten liquid. The outer core is still molten.  With this molten liquid, heavy matter, iron and nickel, sank toward the center, while light matter, oxygen and silicon, moved toward the surface. This process of density stratification formed the layers of the Earth. …and Moon nThe most widely accepted theory for the moon’s origin is the Orpheus theory.  Orpheus theory says that a planet-sized body struck Earth during its early development and sent some of its material into orbit, forming the moon. The Universe, Solar System, and Earth Chapter 3 Pages 3-6 to 3-8

6. MenuPreviousNext 3 - 6 Origin of the Atmosphere and Oceans nWhen the Earth cooled enough for the surface to form a crust, gases from volcanic activity escaped accumulating as an early atmosphere.  The surface was still so hot that when water vapor formed clouds, then rain, the rain boiled off again when it hit the ground.  Finally, the Earth cooled enough to allow the rainwater to accumulate and the oceans formed as water vapor condensed. nThe process that allowed life to form began with development of the oceans.  Carbon dioxide dissolved into young oceans, leaving a nitrogen-rich atmosphere. Scientists think these were the conditions required for life.  Ozone, an oxygen molecule found high in the atmosphere, is also important because it protects life from ultraviolet radiation. nThere was no oxygen in the early atmosphere as it was not needed.  Oxygen, essential to life today, entered the atmosphere about 1.5 billion years ago when photosynthesizing organisms began using carbon dioxide and releasing oxygen. The Universe, Solar System, and Earth Chapter 3 Page 3-8

7. MenuPreviousNext 3 - 7 Abiogenesis nThere is fossil evidence that life began in the ocean. Scientists have found that marine life fossils are significantly older than fossils of terrestrial life.  Cyanobacteria, some of the oldest marine fossils, are dated 3.5 billion years old – this suggests that life began in the sea. nIt is not clear how the first molecules that comprise the building blocks of life originated.  The Urey-Miller experiment (1953) did not produce life, but did prove that basic molecules used by living systems readily form under certain conditions. nRegardless of the exact environment that allowed life to happen, biologists propose that simple molecules randomly combined and separated. Eventually larger, more stable molecules formed by chance.  When one of these combinations became capable of reproducing itself, life was born. nThis origination of life from nonliving matter is called abiogenesis, sometimes referred to as spontaneous generation. The Origins of Life Chapter 3 Pages 3-10 to 3-11

8. MenuPreviousNext 3 - 8 Oxygen and Evolution nHeterotrophs are organisms that rely on consuming compounds to obtain chemical energy. nAutotrophs can create organic chemical energy compounds from inorganic compounds and an external energy source.  The appearance of autotrophs was significant because they break down carbon dioxide into oxygen. nOxygen is important to life because oxygen reactions allow organisms to use chemical energy more effectively. nThe theory of evolution, originally proposed by Charles Darwin, is based on the principle that in nature, various characteristics affect survival. Those with favorable characteristics are more likely than those with less favorable characteristics to survive and reproduce.  The theory of evolution says that over millions of years natural selection and mutation caused the development of all the different life forms and their characteristics.  In other words, organisms became more varied and complex over the millions of years. The Origins of Life Chapter 3 Pages 3-12 & 3-13

9. MenuPreviousNext 3 - 9 Environment Classification Methods nMarine scientists classify marine environments into many different regions based on physical characteristics. They may classify parts of the ocean into different zones or regions based on the light, depth, temperature, density, latitude, and distance from shore or a combination of these. Location nThe most basic division of the ocean based on location is between the water column and the bottom. nThe Pelagic zone is the water column portion. The pelagic zone is divided into two horizontal zones:  1. Neritic zone is the water area between the low tide mark to the edge of the continental shelf.  2. Oceanic zone is the open water area beyond the neritic zone. The oceanic zone is further divided into five vertical regions: the epipelagic zone, the mesopelagic zone, the bathypelagic zone, the abyssalpelagic zone, and the hadalpelagic zone. Ocean Zones and Life Styles Chapter 3 Pages 3-17 & 3-18

10. MenuPreviousNext 3 - 10 Location (continued) nThe five vertical regions of the oceanic zone:  1. Epipelagic zone - top layer sunlight penetrates.  2. Mesopelagic zone - sunlight reaches but not strongly enough to support much life.  3. Bathypelagic zone - deep water in open ocean.  4. Abyssalpelagic zone - even deeper water in oceanic trenches.  5. Hadalpelagic zone - is the deepest water in the ocean trenches. Ocean Zones and Life Styles Chapter 3 Pages 3-18 & 3-19

11. MenuPreviousNext 3 - 11 Location (continued) nThe bottom is the Benthic zone. This zone is divided based on depth-moving from shore to open ocean.  Supralittoral zone - This is the zone that water splashes, but it does not remain submerged.  Littoral zone - The bottom area between the high- and low-tide mark so that it is sometimes submerged and sometimes above water.  Continental shelf - Area beyond the littoral zone. This area is divided further. nSublittoral zone - ocean bottom close to shore. nOuter sublittoral zone - ocean bottom out to edge of continental shelf. nBathyal* zone - is the bottom along the continental slope down to deep open ocean bottom. nAbyssal* zone - deep open ocean bottom. nHadal* zone - deepest zone; below 6,000 meters (19,685 feet). *Also called the deep sea floor. Ocean Zones and Life Styles Chapter 3 Pages 3-19 & 3-20

12. MenuPreviousNext 3 - 12 Marine Lifestyles nMarine life is incredibly diverse. Scientists use groups and subgroups based on common physical characteristics to discuss them.  Plankton are the group of organisms that exist adrift in the ocean currents. nNeuston is an important subgroup of plankton. Neuston are those plankton that float at the surface, for example the Portuguese man-of-war.  Nekton are the organisms that swim, from small invertebrates to large whales. Most of the seas’ predators are nekton. The majority of nekton are vertebrates.  Benthos are organisms that live on or in the bottom. They can move about or be sessile. Sessile organisms are attached to the sea floor. Ocean Zones and Life Styles Chapter 3 Pages 3-20 to 3-22

13. MenuPreviousNext 3 - 13 Marine Lifestyles (continued)  Benthos are divided into: nEpifauna are those animals, such as crabs, that live on the sea floor. nEpiflora are plants, such as seagrasses, that live on the sea floor. nInfauna are organisms that are partially or completely buried in the sea floor, such as clams, sand dollars, tubeworms, and sea pens.  Most infauna are either deposit feeders or suspension feeders. nDeposit feeders feed off detritus drifting down from above. nSuspension feeders filter particles (mostly plankton) suspended in the water for food. Ocean Zones and Life Styles Chapter 3 Page 3-22